This invention relates to a hydraulic shock absorber, and it more particularly relates to a shock absorber having a reserve liquid supply chamber and apparatus for indicating when the chamber is empty.
In the use of liquid shock absorbers as yaw dampers for controlling angular excursions of axles of a railway car, it has been found that if a yaw damper fails because of loss of fluid, the car may not ride properly.
Various systems have been devised for sensing and indicating fluid pressure and the like in a shock absorber, such as is disclosed in the Ellington U.S. Pat. No. 4,141,236. This patent has apparatus for electrically sensing force and velocity and indicating when a combination of these values is outside of a normal range. The Bergeron et al U.S. Pat. No. 4,499,846 discloses an axially operable indicator for attachment to a hydraulic valve to indicate whether the valve is open or closed.
These systems are not applicable to indicate, by snap action, when a reserve liquid supply chamber gradually becomes exhausted in that operation of the indicators is by a gradual change rather than a complete quick change taking affect only when fluid is exhausted from a reserve supply chamber and the chamber must be refilled.
An object of the present invention is to provide a hydraulic shock absorber having a reserve liquid supply chamber and indicator in a manner obviating some of the limitations of the prior systems.
Another object of the present invention is to provide an improved hydraulic shock absorber having a reserve liquid supply chamber and a snap acting indicator to visually indicate when the chamber is empty.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawing, and in part, pointed out as the description of the invention progresses.